The temporal variability in the Hi-C and IRIS data is different.
To begin with, the relative variations are much larger in the IRIS data.
Based on cooling time scales, one would expect a higher temporal variability for emission lines forming at lower temperatures (towards the transition region) as compared to those forming in hotter regions.
This is because radiative and conductive cooling times get longer with increasing temperature [1]}.
Therefore the higher variability in IRIS suggests that the IRIS loops are somewhat cooler than the loops seen in Hi-C.
